The main reason for crack are:

(1) Improper selection of welding rod;

(2) the low level of technology welding operation, the occurrence of incomplete penetration, slag, porosity and other defects; 

(3) Before welding, heat treatment process sub-standard, resulting in welding thermal stress greatly.

Crack Features:

Transverse crack to the welding area or along fusion line and heat affected zone; surface crack is very small, do not polished difficult to find; large crack depth, more depth and repaired zone considerably; welding area high hardness, alloy mostly cable s body or mesh ferrite Caucasus's body.